Lung cancer clinical trials exclude a substantial proportion of patients due to a history of prior cancer, as shown in a new analysis.

Among more than 50 lung cancer clinical trials examined by cancer researchers at the University of Texas Southwestern Medical Center in Dallas, more than 80% excluded patients with prior cancer from participating, according to the study published in the Journal of the National Cancer Institute (2014; doi:10.1093/jnci/dju302). The exclusion criterion was even applied in more than two-thirds of trials in which survival was not the primary end point.

"Our research demonstrates that a substantial proportion of potential subjects are reflexively excluded from lung cancer clinical trials due to prior cancer," said lead author David Gerber, MD, and Associate Professor of Internal Medicine in the division of Hematology and Oncology. In many cases, prior cancer seems to be the only reason for study ineligibility, even though the prior cancer seems unlikely to interfere with the treatment or outcomes of the current lung cancer, Gerber explained.

"The resulting impact on study accrual is sobering," said Gerber, a co-leader of the Experimental Therapeutics Program and co-director of the Lung Disease Oriented Team at the Harold C. Simmons Cancer Center at UT Southwestern. "The proportion of potential patients excluded due to prior cancer per trial ranged up to 18%, with the estimated absolute number of excluded patients per trial ranging up to 207." Gerber projected that these effects will only increase with time; there are currently more than 13 million cancer survivors in the United States, which is a four-fold increase over the past 30 years.

Researchers examined lung cancer trials conducted by the Eastern Cooperative Oncology Group (ECOG), a National Cancer Institute (NCI)-funded organization that designs and conducts cancer clinical trials. Even within this organization, prior cancer eligibility criteria varied widely. They found that 43% of trials excluded patients with prior cancer diagnosis within 5 years of study enrollment, 16% of trials excluded those with active cancer, 14% excluded those with any history of cancer, and 7% of trials excluded patients who had cancer within the past 2 to 3 years.

Nationwide, fewer than 2% of adults participate in clinical trials, with stringent eligibility criteria a key barrier to patient enrollment. Other reasons for low participation include limited access to clinical trials and lack of patient interest.